1. Field of the Invention
The invention relates to stable melamine-polyol dispersions consisting of
(A) 5 to 70 percent by weight of melamine bsed on the total weight of melamine and polyol with 90 percent of the melamine particles having a particle size less than 10 microns,
(B) 95 to 30 percent by weight of a polyol based on the total weight of melamine and polyol, and
(C) 0.001 to 20 percent by weight of at least one stabilizer based on the weight of melamine.
These dispersions are produced by the in situ size reduction with high local energy densities such as 10 to 3000 kilowatt hours per cubic meter and simultaneous dispersion of the melamine in polyols. The dispersions are useful for the manufacture of foamed polyurethane plastics.
2. Prior Art
The preparation of dispersions with organic polymers and hydroxyl group-containing polyethers is well known to those skilled in the art. For this purpose, aqueous polymer dispersions are commonly mixed with polyether polyols followed by the removal of the water. It has also been taught that graft polymers may be produced by the in situ polymerization of ethylenically unsaturated monomers in ethylenically unsaturated polyether polyols which resulting products are then employed for the manufacture of polyurethanes.
According to German Patent Application P 28 50 609.4, stable filler polyol dispersions are obtained when organic or inorganic fillers in the presence of polyols are reduced to particle sizes smaller than 7 microns using high local energy densities during the dispersion process. The use of melamine as a filler is not mentioned in this published application.
The use of melamine as a flame-protection agent for the manufacture of isocyanurate group-containing foamed polyurethane plastics is described in German Published Application Nos. 20 43 917, 23 48 838, and 28 09 084. According to these publications, the melamine is incorporated into the polyol immediately prior to the manufacture of the foam. One drawback is that the melamine polyol mixtures must be processed immediately since the melamine will settle out of solution within a very short period of time.
The purpose of this invention is to produce dispersions of melamine in polyols which can be easily handled, which are stable under storage conditions, and which do not tend toward sedimentation of the dispersed melamine.